U.S. patent number 7,235,188 [Application Number 10/688,900] was granted by the patent office on 2007-06-26 for aqueous phosphoric acid compositions for cleaning semiconductor devices.
This patent grant is currently assigned to EKC Technology, Inc.. Invention is credited to Jerome Daviot, Douglas Holmes, Christopher Reid.
United States Patent |
7,235,188 |
Daviot , et al. |
June 26, 2007 |
Aqueous phosphoric acid compositions for cleaning semiconductor
devices
Abstract
The present invention relates to dilute aqueous solutions
containing phosphoric acid and methods for cleaning plasma etch
residue from semiconductor substrates including such dilute aqueous
solutions. The solution according to the invention may advantageous
contain an alkaline compound, one or more other acid compounds,
and/or a fluoride-containing compound and may optionally contain
additional components such as organic solvents, chelating agents,
amines, and/or surfactants.
Inventors: |
Daviot; Jerome (Glasgow,
GB), Reid; Christopher (Glasgow, GB),
Holmes; Douglas (Bridge of Weir, GB) |
Assignee: |
EKC Technology, Inc. (Hayward,
CA)
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Family
ID: |
32179772 |
Appl.
No.: |
10/688,900 |
Filed: |
October 21, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040137736 A1 |
Jul 15, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60430365 |
Dec 3, 2002 |
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60419968 |
Oct 22, 2002 |
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Current U.S.
Class: |
252/79.1;
134/1.3; 252/79.2; 252/79.3; 252/79.4; 252/79.5; 510/175 |
Current CPC
Class: |
C11D
7/06 (20130101); C11D 7/08 (20130101); C11D
7/3218 (20130101); C11D 7/3227 (20130101); C11D
7/3281 (20130101); C11D 11/0047 (20130101); H01L
21/02071 (20130101) |
Current International
Class: |
C09K
13/00 (20060101) |
Field of
Search: |
;252/79.1,79.2,79.4,79.5
;134/1.3 ;510/175 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Published Application US 2002/0035762 A1, Mar. 2002. cited by
other.
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Primary Examiner: Ahmed; Shamim
Attorney, Agent or Firm: Morgan Lewis & Bockius LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Application
Nos. 60/419,968 filed on Oct. 22, 2002 and 60/430,365 filed on Dec.
3, 2002, the entire contents of each of which are hereby
incorporated by reference
Claims
What is claimed is:
1. An aqueous semiconductor cleaning solution having a pH between
about 1.5 and about 6 and comprising: at least about 75% by weight
of a mixture of water and an organic solvent; from about 0.5% to
about 10% by weight phosphoric acid; optionally one or more other
acid compounds; optionally one or more fluoride-containing
compounds; and at least one alkaline compound selected from the
group consisting of: a trialkylammonium hydroxide and/or a
tetraalkylammonium hydroxide; a hydroxylamine derivative having the
structural formula: ##STR00003## wherein R.sub.3 is hydrogen or a
linear, branched, or cyclic hydrocarbon containing from 1 to 7
carbon atoms; and wherein X and Y are, independently, hydrogen or a
linear, branched, or cyclic hydrocarbon containing from 1 to 7
carbon atoms, or wherein X and Y are linked together form a
nitrogen-containing heterocyclic C.sub.4 C.sub.7 ring; and one or
more alkanolamines having the structural formula: ##STR00004##
wherein R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3 are,
independently in each case, hydrogen or a linear, branched, or
cyclic hydrocarbon containing from 1 to 7 carbon atoms; wherein Z
is a group having the formula
-(-Q-CR.sub.1R.sub.1'--CR.sub.2R.sub.2'--).sub.m--, such that m is
a whole number from 0 to 3 (i.e., when m=0, there is no atom
between the --CR.sub.2R.sub.2'-- group and the --OR.sub.3 group in
the formula above), R.sub.1, R.sub.1', R.sub.2, and R.sub.2' may be
independently defined in each repeat unit, if m>1, within the
parameters set forth for these moieties above, and Q may be
independently defined in each repeat unit, if m>1, each Q being
independently either --O-- or --NR.sub.3--; and wherein X and Y
are, independently in each case, hydrogen, a C.sub.1-C.sub.7
linear, branched, or cyclic hydrocarbon, or a group having the
formula --CR.sub.1R.sub.1'--CR.sub.2R.sub.2'--Z-F, with F being
either --O--R.sub.3 or --NR.sub.3R.sub.4, where R.sub.4 is defined
similarly to R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3
above, and with Z, R.sub.1, R.sub.1', R.sub.2, R.sub.2', and
R.sub.3 defined as above, or wherein X and Y are linked together
form a nitrogen-containing heterocyclic C.sub.4 C.sub.7 ring.
2. The aqueous semiconductor cleaning solution of claim 1, wherein
the pH of the solution is between about 2 and about 6.
3. The aqueous semiconductor cleaning solution of claim 1, wherein
the at least one alkaline component comprises a hydroxlyamine
derivative present in an amount from about 0.3% to about 1% by
weight.
4. The aqueous semiconductor cleaning solution of claim 1, wherein
the at least one alkaline component comprises hydroxylamine or
N,N-diethylhydroxylamine.
5. The aqueous semiconductor cleaning solution of claim 1, wherein
the at least one alkaline component comprises a tri-alkylammonium
hydroxide or tetra-alkylammonium hydroxide present in an amount
from about 0.5% to about 3% by weight.
6. The aqueous semiconductor cleaning solution of claim 5, wherein
the at least one alkaline component comprises choline
hydroxide.
7. The aqueous semiconductor cleaning solution of claim 1, which
comprises one or more other acid compounds selected from the group
consisting of hydrochloric acid, nitric acid, periodic acid,
pyrophosphoric acid, fluorosilicic acid, sulfuric acid,
methanesulfonic acid, oxalic acid, lactic acid, citric acid,
xylenesulfonic acid, toluenesulfonic acid, formic acid, tartaric
acid, propionic acid, benzoic acid, ascorbic acid, gluconic acid,
malic acid, malonic acid, succinic acid, gallic acid, butyric acid,
trifluoracetic acid, and mixtures thereof.
8. The aqueous semiconductor cleaning solution of claim 1, wherein
the aqueous semiconductor cleaning solution comprises one or more
other acid compounds selected from glycolic acid, methanesulfonic
acid, pyrophosphoric acid, oxalic acid, lactic acid, and citric
acid.
9. The aqueous semiconductor cleaning solution of claim 8, wherein
the one or more other acids are present in an amount from about
0.2% to about 5% by weight.
10. The aqueous semiconductor cleaning solution of claim 1, wherein
the aqueous semiconductor cleaning solution comprises one or more
fluorine-containing compounds present in an amount from about 0.01%
to about 0.1% by weight.
11. The aqueous semiconductor cleaning solution of claim 1, wherein
the aqueous semiconductor cleaning solution comprises one or more
fluorine-containing compounds comprising ammonium bifluoride and/or
ammonium fluoride.
12. The aqueous semiconductor cleaning solution of claim 1, wherein
the organic solvent is in an amount from about 5% to about 15% by
weight.
13. The aqueous semiconductor cleaning solution of claim 12,
wherein the organic solvent comprises an organic acid ester.
14. The aqueous semiconductor cleaning solution of claim 1,
comprising a surfactant.
15. The aqueous semiconductor cleaning solution of claim 1, wherein
the at least one alkaline compound includes one or more
alkanolamines selected from the group consisting of
monoethanolamine, 2-(2-hydroxylethylamino)ethanol,
2-(2-aminoethoxy)ethanol, N,N,N-tris(2-hydroxyethyl)-ammonia,
isopropanolamine, 3-amino-1-propanol, 2-amino-1-propanol,
2-(N-methylamino)ethanol, 2-(2-aminoethylamino)ethanol, and
mixtures thereof.
16. The aqueous semiconductor cleaning solution of claim 1, wherein
the at least one alkaline compound includes one or more
alkanolamines present in an amount from about 0.5% to about 5% by
weight.
17. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution is substantially free from other acid compounds.
18. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution is substantially free from fluoride-containing
compounds.
19. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution is substantially free from alkanolamines.
20. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution contains substantially no additional components.
21. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution is substantially free from hydroxylamine
derivatives.
22. The aqueous semiconductor cleaning solution of claim 1, wherein
the solution is substantially free from organic solvents.
23. The aqueous semiconductor cleaning solution of claim 1, wherein
the concentration of water is at least about 85% by weight.
24. A dilute aqueous semiconductor cleaner and residue remover
having a pH between about 1.5 and about 6 and comprising: a mixture
of water and one or more polar organic solvents, present in an
amount of at least about 75% by weight; phosphoric acid or salt
thereof, present in an amount from about 0.1% to about 6% by weight
of 85% phosphoric acid; hydroxylamine or a hydroxylamine
derivative, present in the solution in an amount from about 0.1% to
about 5% by weight not including the counterion of the
hydroxylamine derivative salt, if present; optionally, a
tri-alkylammonium hydroxide and/or tetra-alkylammonium hydroxide,
present in the solution in an amount from about 0.2% to about 5% by
weight; optionally, an alkanolamine, present in the solution in an
amount from about 0.2% to about 5% by weight; optionally, a
fluoride-containing compound, present in the solution in an amount
from about 0.001% to about 0.5% by weight; optionally, an other
acid compound, present in the solution in an amount from about
0.05% to about 6% by weight; optionally, a chelating agent, present
in the solution in an amount from about 0.1% to about 8% by weight;
and optionally, a surfactant, present in the solution in an amount
from about 0.01% to about 3% by weight.
25. The dilute aqueous cleaner and residue remover of claim 24,
wherein the cleaner and residue remover consists essentially of:
water; one or more polar organic solvents; about 1.5% to about 2.5%
by weight of phosphoric acid; about 0.5% to about 1% by weight of a
hydroxylamine or hydroxylamine derivative; and about 0.005% to
about 0.04% by weight of a fluoride-containing compound, and
wherein the cleaner and residue remover is substantially free from
surfactants.
26. The dilute aqueous cleaner and residue remover of claim 24,
wherein the cleaner and residue remover consists essentially of:
one or more polar organic solvents; about 1.5% to about 2.5% by
weight of phosphoric acid; about 0.5% to about 1% by weight of a
hydroxylamine derivative; about 0.005% to about 0.04% by weight of
a fluoride-containing compound; and about 0.05% to about 0.2% by
weight of a surfactant.
27. A dilute aqueous cleaner and residue remover consisting
essentially of: one or more polar organic solvents: about 1.5% to
about 2.5% by weight of phosphoric acid; about 0.5% to about 1% by
weight of a hydroxylamine or hydroxylamine derivative; and about
0.005% to about 0.1% by weight of a fluoride-containing
compound.
28. A dilute aqueous cleaner and residue remover consisting
essentially of: about 1.5% to about 2.5% by weight of phosphoric
acid; about 0.5% to about 1% by weight of a hydroxylamine
derivative; about 0.005% to about 0.1% by weight of a
fluoride-containing compound; and about 5% to about 15% by weight
of a polar organic solvent.
29. A dilute aqueous semiconductor cleaner and residue remover
consisting essentially of: 1.5% to about 2.5% by weight of
phosphoric acid; and 0.5% to about 1.5% by weight of a
tri-alkylammonium salt and/or tetra-alkylammonium salt.
30. A dilute aqueous cleaner and residue remover having a pH
between about 1.5 and about 6 consisting essentially of: about 1.5%
to about 4% by weight of 85% phosphoric acid; about 0.3% to about
4% by weight of oxalic acid dihydrate; about 0.3% to about 4% by
weight of a monofunctional organic acid; about 90% to about 99% by
weight of water; and optionally between about 0.1% and about 1% of
a chelator, wherein the formulation contains substantially no
organic solvents and no compounds listed as SARA 3 hazardous
compounds on the filing date of this application.
31. A dilute aqueous cleaner and residue remover consisting
essentially of: about 0.5% to about 6% by weight of 85% phosphoric
acid; about 2% to about 12% by weight of oxalic acid dihydrate;
optionally about 0.2% to about 15% by weight of a monofunctional
organic acid; optionally between about 0.05% and 1.5% by weight of:
ammonium hydroxide, an alkyl ammonium hydroxide substituted with 2
or 3 alkyl moieties independently selected from methyl and ethyl
moieties, or a mixture thereof; optionally between about 0.1% and
about 1% of a chelator; and water, wherein the pH of the cleaner
and residue remover is between 1.5 and 9, and the cleaner and
residue remove contains substantially no organic solvents and no
compounds listed as SARA 3 hazardous compounds on the filing date
of this application.
32. A dilute aqueous cleaner and residue remover consisting
essentially of: about 1.5% to about 4% by weight of 85% phosphoric
acid; about 1% to about 4% by weight of glycolic acid; and about
92% to about 97.5% by weight of water.
33. The semiconductor cleaning solution of claim 32, wherein the
solution is substantially free from: alkanolamines, quaternary
ammonium compounds, hydroxylamine and hydroxylamine derivatives,
other acid compounds, fluoride-containing compounds, organic
solvents, non-hydroxyl-containing amines, chelating agents, and
surfactants.
34. A dilute aqueous cleaner and residue remover consisting
essentially of: about 3% to about 6% by weight of 85% phosphoric
acid; about 1% to about 2% by weight of glycolic acid; and about
92% to about 96% by weight of water.
35. The semiconductor cleaning solution of claim 34, wherein the
solution is substantially free from: alkanolamines, quaternary
ammonium compounds, hydroxylamine and hydroxylamine derivatives,
other acid compounds, fluoride-containing compounds, organic
solvents, non-hydroxyl-containing amines, chelating agents, and
surfactants.
Description
FIELD OF THE INVENTION
The present invention relates to dilute aqueous solutions
containing phosphoric acid and methods for cleaning plasma etch
residue from semiconductor substrates including such dilute aqueous
solutions. The compositions and methods according to the invention
can advantageously provide both cleaning efficiency and material
compatibility.
BACKGROUND OF THE INVENTION
Cleaners are needed during semiconductor fabrication, and one
well-known family of cleaners known as HDA.RTM. is available from
EKC Technology.
SUMMARY OF THE INVENTION
Dilute aqueous solutions of phosphoric acid in combination with
alkaline compounds and/or acids can conveniently be used to clean
plasma ash residues from semiconductor substrates. Cleaners are
needed during semiconductor fabrication, and one well-known family
of cleaners known as HDA.RTM. is available from EKC Technology.
Phosphoric acid is readily available as an 85% solution of
H.sub.3PO.sub.4 in water. In this specification concentrations of
phosphoric acid are specified as the per cent by weight of an 85%
solution of H.sub.3PO.sub.4 in water, e.g., a concentration of
about 2% is equivalent to about 1.7% H.sub.3PO.sub.4.
Concentrations of other compounds are specified on 100% basis, even
if the compound is ordinarily supplied as an aqueous solution
(e.g., hydroxylamine is typically supplied as a 50% solution in
water).
The present invention involves an aqueous semiconductor cleaning
solution comprising: at least about 75%, alternately at least about
85%, by weight water; from about 0.5% to about 10% by weight
phosphoric acid; and at least one alkaline compound selected from
the group consisting of a quaternary ammonium hydroxide, a
hydroxylamine derivative, an a mixture thereof. Optionally, the
solution may also contain one or more other acid compounds, one or
more fluoride-containing compounds, and/or one or more
alkanolamines. Advantageously, the pH of the solution can be
between about 2 and about 6.
In one embodiment, the at least one alkaline component includes a
hydroxlyamine derivative present in an amount from about 0.3% to
about 1% by weight. In another embodiment, the at least one
alkaline component includes, and preferably is, hydroxylamine or
N,N-diethylhydroxylamine.
In another embodiment, the at least one alkaline component includes
a quaternary ammonium compound present in an amount from about 0.5%
to about 3% by weight. In another embodiment, the at least one
alkaline component includes, and preferably is, choline
hydroxide.
In another embodiment, the optional one or more other acid
compounds is present and may include hydrochloric acid, nitric
acid, periodic acid, pyrophosphoric acid, fluorosilicic acid,
sulfuric acid, methanesulfonic acid, oxalic acid, lactic acid,
citric acid, xylenesulfonic acid, toluenesulfonic acid, formic
acid, tartaric acid, propionic acid, benzoic acid, ascorbic acid,
gluconic acid, malic acid, malonic acid, succinic acid, gallic
acid, butyric acid, trifluoracetic acid, or mixtures thereof.
Alternately or preferably, the one or more other acid compounds
includes, and preferably is, glycolic acid, methanesulfonic acid,
pyrophosphoric acid, oxalic acid, lactic acid, or citric acid. In
another embodiment, the one or more other acids can be present in
an amount from about 0.2% to about 5% by weight.
In yet another embodiment, the optional one or more
fluorine-containing compounds is present in an amount from about
0.01% to about 0.1% by weight. In still another embodiment, the one
or more fluorine-containing compounds includes, and preferably is,
ammonium bifluoride and/or ammonium fluoride.
In one embodiment, the solution can further include an organic
solvent in an amount from about 5% to about 15% by weight. In
another embodiment, the organic solvent includes an organic acid
alkyl ester.
In another embodiment, the solution can further include a
surfactant.
In yet another embodiment, the solution can further include one or
more alkanolamines, preferably monoethanolamine,
2-(2-hydroxylethylamino)ethanol, 2-(2-aminoethoxy)ethanol,
N,N,N-tris(2-hydroxyethyl)-ammonia, isopropanolamine,
3-amino-1-propanol, 2-amino-1-propanol, 2-(N-methylamino)ethanol,
2-(2-aminoethylamino)ethanol, or a mixture thereof. In still
another embodiment, the one or more alkanolamines is present in an
amount from about 0.5% to about 5% by weight.
In alternate embodiments, the solution can be substantially free
from one or more of the following: other acid compounds,
fluoride-containing compounds, alkanolamines, hydroxylamine
derivatives, organic solvents, and a combination thereof. In
another alternate embodiment, the solution can contain
substantially no additional components.
DEFINITIONS
Unless otherwise specified, all percentages expressed herein should
be understood to refer to percentages by weight. Also, the term
"about," when used in reference to a range of values, should be
understood to refer to either value in the range, or to both values
in the range.
As used herein, the phrases "contains substantially no" and
"substantially free from," in reference to a composition means:
for major components including other acid components (not
phosphoric acid), polar organic solvents including
non-hydroxyl-containing amines, water, organic solvents,
hydroxylamine and hydroxylamine derivatives, the aforementioned
phrases should be understood to mean that the composition contains
less than 1.5%, preferably less than about 1%, more preferably less
than about 0.1%, of the specific element mentioned thereafter;
for minor components including chelating agents, corrosion
inhibitors, fluoride-containing compounds, surfactants, and the
like, the aforementioned phrases should be understood to mean that
the composition contains less than about 0.1%, preferably less than
about 0.01%, most preferably less than about 0.005%, of the
specific element mentioned thereafter; and
for trace contaminants such as metals or metal ions, the
aforementioned phrases should be understood to mean that the
composition contains less than about 50 ppm, preferably less than
about 10 ppm.
Preferably, when one of the aforementioned phrases is used, the
composition is completely free of any added element specifically
mentioned thereafter, or at least does not contain the added
element in an amount such that the element affects the efficacy,
storability, usability regarding necessary safety concerns, or
stability of the composition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Dilute aqueous solutions of phosphoric acid in combination with
alkaline compounds and/or acids can conveniently be used to clean
plasma ash residues from semiconductor substrates. Cleaners and
residue removers that are dilute and that contain relatively
inexpensive components are desired in the industry, because the
cost of producing cleaners and residue removers is largely driven
by the high cost of components contained therein. Similarly, dilute
cleaners and residue removers are more easily disposed of,
especially if most or all components therein are relatively
non-toxic. Finally, dilute cleaners are less susceptible to change
in properties from the evaporation of small quantities of
water.
In one embodiment the invention is a cleaning and residue removing
composition comprising:
a polar solvent, preferably water, but optionally polar organic
solvent(s) or mixtures of water and polar organic solvent(s),
wherein the polar solvent is present at least about 75%,
alternately at least about 85%, and in a preferred embodiment at
least about 92% polar solvent, for example at least about 94% by
weight water;
phosphoric acid or salt thereof, wherein the phosphoric acid or
salt thereof is present in an amount from about 0.01% to about 10%,
preferably from about 0.1% to about 6%, more preferably from about
1% to about 4%, for example between about 1.7% to about 2.5% by
weight of 85% phosphoric acid;
optionally, an alkaline compound, such as a quaternary ammonium
compound as described herein, preferably choline hydroxide, choline
derivatives such as bis and tris choline, or mixtures thereof,
present in the solution in an amount from about 0.2% to about 5%,
preferably from about 0.5% to about 3%, for example from about 1%
to about 2.5% by weight;
optionally, an alkaline compound, such as a hydroxylamine
derivative, preferably hydroxylamine or diethylhydroxylamine,
present in the solution in an amount from about 0.1% to about 5%,
preferably from about 0.2% to about 3%, for example from about 0.5%
to about 1%, by weight not including the counterion of the salt if
present;
optionally, an alkaline compound, such as an alkanolamine as
described herein, preferably AEEA, present in the solution in an
amount from about 0.2% to about 5%, preferably from about 0.5% to
about 3%, for example from about 1% to about 2.5% by weight;
optionally, a fluoride-containing compound, such as hydrogen
fluoride, ammonium fluoride, ammonium biflouride, or mixtures
thereof, present in the solution in an amount from about 0.001% to
about 0.5%, preferably from about 0.005% to about 0.1%, for example
from about 0.01% to about 0.05% by weight;
optionally, another acid compound, such as an inorganic acid like
pyrophosphoric acid, periodic acid, or fluorosilicic acid, an
organic acid like citric acid, lactic acid, glycolic acid, oxalic
acid, a hybrid acid like methanesulfonic acid, or mixture thereof,
present in the solution in an amount from about 0.05% to about 6%,
preferably from about 0.2% to about 4%, for example from about 0.5%
to about 2% by weight;
optionally, a chelating agent, for example catechol, EDTA, DTPA, or
mixtures thereof, present in the solution in an amount from about
0.1% to about 8%, for example from about 0.5% to about 2% by
weight;
optionally, an amine (that is not hydroxylamine derivative or
alkanolamine), present in the solution in an amount from about 0.1
% to about 20%, for example from about 0.5% to about 4% by weight;
and
optionally, a surfactant, for example an epoxy-polyamide compound,
present in the solution in an amount from about 0.01% to about 3%,
for example from about 0.1% to about 0.5% by weight.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of: about 1.5% to about 2.5% by weight of phosphoric
acid; about 0.5% to about 1% by weight of a hydroxylamine
derivative, preferably hydroxylamine; and about 0.005% to about
0.04% by weight of a fluoride-containing compound, preferably
ammonium bifluoride.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of: about 1.5% to about 2.5% by weight of phosphoric
acid; about 0.5% to about 1% by weight of a hydroxylamine
derivative, preferably hydroxylamine; about 0.005% to about 0.04%
by weight of a fluoride-containing compound, preferably ammonium
bifluoride; and about 0.05% to about 0.2% by weight of a
surfactant, preferably an epoxy-polyamide compound.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of: about 1.5% to about 2.5% by weight of phosphoric
acid; about 0.5% to about I% by weight of a hydroxylamine
derivative, preferably hydroxylamine; and about 0.005 % to about
0.1% by weight of a fluoride-containing compound, preferably
ammonium fluoride.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of: about 1.5% to about 2.5% by weight of phosphoric
acid; about 0.5% to about 1% by weight of a hydroxylamine
derivative, preferably hydroxylamine; about 0.005% to about 0.1% by
weight of a fluoride-containing compound, preferably ammonium
fluoride; and about 5% to about 15% by weight of a polar organic
solvent, preferably an organic acid alkyl ester such as ethyl
lactate.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of about 1.5% to about 2.5% by weight of phosphoric
acid and about 0.5% to about 1.5% by weight of a quaternary
ammonium salt, preferably choline hydroxide.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of: about 1.5% to about 4% by weight of phosphoric
acid; and about 1% to about 4% by weight of an other acid compound,
preferably an organic acid such as oxalic acid, lactic acid, citric
acid, glycolic acid, or a mixture thereof.
In one preferred embodiment, the dilute aqueous cleaner consists
essentially of:
about 1.5% to about 4%, more preferably between about 1.7% to about
2.5%, for example about 2% by weight of 85% phosphoric acid;
about 0.3% to about 4%, more preferably between about 0.5% to about
2%, for example about 1% by weight of a first organic acid
compound, preferably a difunctional organic acid, such as oxalic
acid dihydrate;
about 0.3% to about 4%, more preferably between about 0.5% to about
2%, for example about 1% by weight of a second organic acid
compound which is different than the first organic acid compound,
preferably a monofunctional organic acid, such as formic acid;
and
between about 90% and about 99%, more preferably between about 93
and 98%, for example about 96%, by weight of water. Such
composition has substantially no organic solvents, substantially no
SARA 3 hazardous compounds, exhibits very little corrosion on ST
formulations. Optionally the composition may contain between about
0.1% and about 1% of a chelator, such as EDTA.
Other dilute aqueous cleaner compositions consists essentially
of:
optionally about 0.5% to about 6% by weight of 85% phosphoric
acid;
about 2% to about 12%, more preferably between about 3% to about
10% by weight of a first organic acid compound, preferably a
difunctional organic acid, such as oxalic acid dihydrate;
optionally about 0.2% to about 15%, more preferably between about
6% to about 12% by weight of a second organic acid compound which
is different than the first organic acid compound, preferably a
monofunctional organic acid, such as formic acid;
optionally between about 0.05% and 1.5%, more preferably between
about 0.5% to about 1.5% of an ammonium salt, for example ammonium
hydroxide, an alkyl ammonium hydroxide substituted with 2 or 3,
preferably 3, alkyl moieties independently selected from methyl and
ethyl moieties, for example tetramethyl ammonium hydroxide, or a
mixture thereof;
between about 80% and about 94% water. Such composition has
substantially no organic solvents, substantially no SARA 3
hazardous compounds, exhibits very little corrosion on ST
formulations. Optionally the composition may contain between about
0.1 % and about 1% of a chelator, such as EDTA.
Phosphoric acid is readily available as an 85% solution of
H.sub.3PO.sub.4 in water. In this specification concentrations of
phosphoric acid are specified as the per cent by weight of an 85%
solution of H.sub.3PO.sub.4 in water, e.g., a concentration of
about 2% is equivalent to about 1.7% H.sub.3PO.sub.4. Unless
specifically stated, concentrations of other compounds are
specified on 100% basis, even if the compound is ordinarily
supplied as an aqueous solution (e.g., hydroxylamine is typically
supplied as a 50% solution in water).
The present invention involves an aqueous semiconductor cleaning
solution comprising: at least about 75%, alternately at least about
85%, by weight water; from about 0.5% to about 10% by weight
phosphoric acid; and at least one alkaline compound selected from
the group consisting of a quaternary ammonium hydroxide, a
hydroxylamine derivative, an a mixture thereof. Optionally, the
solution may also contain one or more other acid compounds, one or
more fluoride-containing compounds, and/or one or more
alkanolamines. Advantageously, the pH of the solution can be
between about 2 and about 6.
Concentrations of phosphoric acid up to 10% are useful for
cleaning, according to the principles of this invention, although
concentrations of about 0.5% to about 6%, preferably about 2% to
about 3%, by weight are preferred when considering cleaning
ability, material compatibility, and cost. In other embodiments,
the concentration of phosphoric acid may alternately be from about
1% to about 8% by weight, from about 2% to about 6% by weight, from
about 1% to about 4% by weight.
In this specification, dilute aqueous solutions is defined as
containing at least about 75% by weight water, preferably at least
about 85% by weight, for example at least about 90% by weight or at
least about 95% by weight. In one embodiment, the concentration of
water in the solutions according to the invention is from about 75%
to about 95% by weight. In another embodiment, the concentration of
water in the solutions according to the invention is from about 80%
by to about 90% by weight.
In one embodiment, the dilute aqueous solution containing
phosphoric acid according to the invention is substantially free of
abrasive particles such as typical metal oxide abrasives (e.g.,
alumina, silica, ceria, zirconia, magnesia, and the like).
Alkaline Compounds
Dilute aqueous solutions of phosphoric acid may also contain
alkaline compounds for improved utility as cleaners. Exemplary
alkaline compounds include, but are not limited to, quaternary
ammonium compounds, hydroxylamine or hydroxylamine derivatives,
alkanolamines, and mixtures thereof. In some embodiments, an amine
can be used as an alkaline compound. In other embodiments, amines
qualify only as other additive components.
Exemplary quaternary ammonium compounds include, but are not
limited to, ammonium hydroxide; alkylammonium compounds such as
monoalkylammonium hydroxide, dialkylammonium hydroxide,
trialkylammonium hydroxide, and/or tetraalkylammonium hydroxides
(e.g., tetramethylammonium hydroxide, choline hydroxide,
di(2-hydroxyethyl)dimethylammonium hydroxide,
tris(2-hydroxyethyl)methylammonium hydroxide, and the like, and
mixtures thereof); and mixtures thereof. While the hydroxide
counterion is preferred for these quaternary ammonium compounds,
other alternate counterions are also contemplated, including, but
not limited to, bisulfite, sulfite, sulfate, nitrate, nitrite,
phosphate, phosphite, carbonate, trifluoroacetate, organic
carboxylates from organic acids such as those listed herein, and
the like, and combinations thereof. Compounds containing two or
more ammonium moieties are also useful, both as a cleaning additive
and as a chelating agent.
Exemplary hydroxylamine derivatives satisfy the general
formula:
##STR00001## wherein R.sub.3 is hydrogen or a linear, branched, or
cyclic hydrocarbon containing from 1 to 7 carbon atoms; and wherein
X and Y are, independently, hydrogen or a linear, branched, or
cyclic hydrocarbon containing from 1 to 7 carbon atoms, or wherein
X and Y are linked together form a nitrogen-containing heterocyclic
C.sub.4 C.sub.7 ring.
Examples of derivatives of hydroxylamine according to the invention
include, but are in no way limited to, hydroxylamine;
alkylhydroxylamines such as N-methyl-hydroxylamine,
N,N-dimethyl-hydroxylamine, N-ethyl-hydroxylamine,
N,N-diethyl-hydroxylamine, methoxylamine, ethoxylamine,
N-methyl-methoxylamine, N-isopropylhydroxylamine, and the like, and
mixtures thereof. It should be understood that hydroxylamine and
its derivatives, as defined above, are available (and may be
included in a composition according to the invention) as above, as
salts (e.g., sulfate salts, nitrate salts, phosphate salts, or the
like), or as a combination thereof. In the present invention, these
hydroxylamine salts and their derivatives should be characterized
as hydroxylamine derivatives herein, and not as quaternary ammonium
compounds.
Alkanolamines according to the invention may advantageously be
those two-carbon atom linkage alkanolamines having the following
formula:
##STR00002##
wherein R.sub.1, R.sub.1, 'R.sub.2, R.sub.2', and R.sub.3 are,
independently in each case, hydrogen or a linear, branched, or
cyclic hydrocarbon containing from 1 to 7 carbon atoms; wherein Z
is a group having the formula
-(-Q-CR.sub.1R.sub.1'--CR.sub.2R.sub.2'--).sub.m--, such that m is
a whole number from 0 to 3 (i.e., when m=0, there is no atom
between the --CR.sub.2 R.sub.2'-- group and the --OR.sub.3 group in
the formula above), R.sub.1, R.sub.1,'R.sub.2, and R.sub.2' may be
independently defined in each repeat unit, if m>1, within the
parameters set forth for these moieties above, and Q may be
independently defined in each repeat unit, if m>1, each Q being
independently either --O-- or --NR.sub.3--; and wherein X and Y
are, independently in each case, hydrogen, a C.sub.1 C.sub.7
linear, branched, or cyclic hydrocarbon, or a group having the
formula --CR.sub.1 R.sub.1'--CR.sub.2 R.sub.2'-Z-F, with F being
either --O--R.sub.3 or --NR.sub.3R.sub.4, where R.sub.4 is defined
similarly to R.sub.1, R.sub.1', R.sub.2, R.sub.2', and R.sub.3
above, and with Z, R.sub.1, R.sub.1', R.sub.2, R.sub.2', and
R.sub.3 defined as above, or wherein X and Y are linked together
form a nitrogen-containing heterocyclic C.sub.4 C.sub.7 ring.
Exemplary alkanolamines include, but are not limited to,
monoethanolamine, 2-(2-hydroxylethylamino)ethanol (i.e.,
diethanolamine or DEA), 2-(2-aminoethoxy)ethanol (i.e.,
diglycolamine or DGA), N,N,N-tris(2-hydroxyethyl)-ammonia (i.e.,
triethanolamine or TEA), isopropanolamine, 3-amino-1-propanol
(i.e., n-propanolamine or NPA), 2-amino-1 -propanol
("monoisopropanolamine" or "MIPA"), 2-(N-methylamino)ethanol (i.e.,
monomethylethanolamine or MMEA), 2-(2-aminoethylamino)ethanol
(i.e., aminoethylaminoethanol or AEEA), and mixtures thereof.
Choline hydroxide and hydroxylamine are preferred alkaline
compounds. In an alternate preferred embodiment, an alkanolamine
can be a preferred alkaline compound.
In one embodiment, alkaline compounds according to the invention
may be present in the solution in an amount from about 0.5% to
about 5%, alternately from about 0.5% to about 3%, from about 1% to
about 3%, from about 0.2% to about 1.5%, from about 0.2% to about
2%, from about 0.2% to about 1%, from about 0.5% to about 1.5%,
from about 1.5% to about 3%, or from about 1.5% to about 2.5%.
In another embodiment, the solution according to the invention can
be substantially free from alkaline compounds. In still another
embodiment, the solution according to the invention can be
substantially free from alkanolamines, but may contain quaternary
ammonium compounds and/or hydroxylamine or hydroxylamine
derivatives. In yet another embodiment, the solution according to
the invention can be substantially free from hydroxylamine or
hydroxylamine derivatives, but may contain quaternary ammonium
compounds and/or alkanolamines. In yet another embodiment, the
solution according to the invention can be substantially free from
quaternary ammonium compounds, but may contain hydroxylamine or
hydroxylamine derivatives and/or alkanolamines. In yet another
embodiment, the solution according to the invention can be
substantially free from quaternary ammonium compounds and
hydroxylamine or hydroxylamine derivatives, but may contain
alkanolamines. In yet another embodiment, the solution according to
the invention can be substantially free from quaternary ammonium
compounds and alkanolamines, but may contain hydroxylamine or
hydroxylamine derivatives. In yet another embodiment, the solution
according to the invention can be substantially free from
alkanolamines and hydroxylamine or hydroxylamine derivatives, but
may contain quaternary ammonium compounds.
Other Acids
Dilute aqueous solutions of phosphoric acid may also include other
acid compounds for improved utility as cleaners. Exemplary acids
include, but are not limited to, other inorganic acids such as
hydrochloric acid, nitric acid, periodic acid, pyrophosphoric acid,
fluorosilicic acid, sulfuric acid, and the like, and mixtures
thereof; organic acids such as oxalic acid, lactic acid, citric
acid, formic acid, tartaric acid, propionic acid, benzoic acid,
ascorbic acid, gluconic acid, malic acid, malonic acid, succinic
acid, gallic acid, butyric acid, and the like, and mixtures
thereof; other hybrid acids such as methanesulfonic acid,
xylenesulfonic acid, toluenesulfonic acid, trifluoracetic acid, and
the like, and mixtures thereof; and mixtures thereof.
In one embodiment, the other acid compounds according to the
invention may be present in the solution in an amount from about
0.5% to about 5%, alternately from about 0.5% to about 3%, from
about 1% to about 3%, from about 0.2% to about 1.5%, from about
0.2% to about 2%, from about 0.2% to about 1%, from about 0.5% to
about 1.5%, from about 1.5% to about 3%, or from about 1.5% to
about 2.5%.
The multifunctional carboxylic acids (i.e., compounds having two or
more, alternately three or more, carboxylic acid functional groups
on the same molecule) are preferred acids.
In another embodiment, the solution according to the invention can
be substantially free from other acid compounds.
Fluoride Compounds
The dilute aqueous solutions of phosphoric acid may also include a
fluoride compound for improved utility as cleaners. Suitable
fluoride compounds include, but are not limited to, ammonium
fluoride, ammonium bifluoride, hydrogen fluoride, alkylammonium
fluoride, alkylammonium bifluoride, and the like, and mixtures
thereof. In another embodiment, the solution according to the
invention can be substantially free from fluoride-containing
compounds.
In one embodiment, the fluoride-containing compound is present in
the solution in an amount from about 0.001% to about 0.5%,
preferably from about 0.005% to about 0.1%, for example from about
0.01% to about 0.05% by weight.
Other Components
The dilute aqueous solutions of phosphoric acid may optionally
contain additional components such as organic solvents, chelating
agents (e.g., those not qualifying as other acid compounds), amines
(e.g., those not qualifying as quaternary ammonium compounds,
hydroxylamine or hydroxylamine derivatives, or alkanolamines, as
described above), and/or surfactants. In one embodiment, additional
components including, but not limited to, those enumerated above
may be added to the solution to achieve a specific goal. In another
embodiment, the dilute aqueous solution according to the invention
contains substantially no additional components.
Organic solvents may be either polar or non-polar. Generally,
non-polar organic solvents are not preferred, though high boiling
alcohols and the like may be used. Examples of polar organic
solvents for the composition according to the invention include,
but are in no way limited to, dimethyl sulfoxide, ethylene glycol,
organic acid alkyl (e.g., C.sub.1 C.sub.6) esters such as ethyl
lactate, ethylene glycol alkyl ether, diethylene glycol alkyl
ether, triethylene glycol alkyl ether, propylene glycol, propylene
glycol alkyl ether, dimethyl sulfoxide, N-substituted pyrrolidone
such as N-methyl-2-pyrrolidone (NMP), sulfolanes,
dimethylacetamide, and the like, or any combination thereof. In one
embodiment where polar organic solvents are present, the boiling
point of the polar organic solvent(s) is(are) at least about
85.degree. C., alternately at least about 90.degree. C. or at least
about 95.degree. C. Care must be taken because, in the absence of
alkanolamines and the like, certain organic solvent may be only
slightly miscible with the water of the aqueous phosphoric acid
solution according to the invention.
In one embodiment, an organic solvent is present in the solution
according to the invention in an amount from about 2% to about 15%,
alternately from about 5% to about 15%, from about 8% to about 12%,
from about 7% to about 15%, from about 3% to about 10%, or from
about 4% to about 13%.
According to the present invention, amines, particularly
alkanolamines and also particularly low molecular weight amines,
are separate from, and are not classified as, a polar organic
solvent. Other additional polar organic solvents as known in the
art, other than those specifically excluded, can also be used in
the composition of the present invention. In an alternate
embodiment, the composition according to the invention is
substantially free from organic solvents as defined herein.
Examples of chelating agents include, but in no way limited to,
mono-, di-, or multi-hydroxybenzene-type compounds, e.g., such as
catechol, resorcinol, butylated hydroxytoluene ("BHT"), and the
like, or a combination thereof. In one embodiment the chelators
include three or more carboxylic acid-containing moieties, e.g.,
such as ethylenediamine tetraacetic acid ("EDTA"), non-metallic
EDTA salts, and the like, or a combination thereof. Compounds
containing a two carboxylic acid moieties are less preferred.
Compounds containing both hydroxyl and carboxylic acid moieties are
useful in one embodiment. Aromatic compounds containing thiol
groups, e.g., such as thiophenol; amino-carboxylic acids; diamines,
e.g., such as ethylene diamine; polyalcohols; polyethylene oxide;
polyamines; polyimines; or a combination thereof, are useful in one
embodiment. In one embodiment, one or more chelating agents can be
used in one composition, where the chelating agents are selected
from groups described above. Alternately or additionally, some
chelating agents are described in U.S. Pat. No. 5,417,877, issued
May 23, 1995 to Ward, and in commonly assigned U.S. Pat. No.
5,672,577, issued Sept. 30, 1997 to Lee, the disclosures of each of
which are incorporated herein by reference. In an alternate
embodiment, the composition is substantially free from chelating
agents.
In one embodiment, a chelating agent is present in the solution
according to the invention in an amount from about 0.1% to about
10%, alternately from about 1% to about 10%, from about 0.5% to
about 5%, from about 0.5% to about 3%, from about 0.1% to about 2%,
or from about 1% to about 3%.
In one embodiment, the composition according to the invention
optionally contains an amine compound that is not a
hydroxyl-containing amine and is not an alkanolamine. Examples of
such amine compounds include, but are in no way limited to,
o-diaminobenzene, p-diaminobenzene,
N-(2-aminoethyl)-ethylenediamine ("AEEDA"), piperazine,
N-substituted piperazine derivatives, piperidine, N-substituted
piperidine derivatives, diethylene triamine,
2-methyleneaminopropylenediamine, hexamthylene tetramine, and the
like, or a combination thereof. Amines may increase corrosion of
certain sensitive metals. In an alternate embodiment, the
composition according to the invention is substantially free from
non-hydroxyl-containing amine compounds.
In one embodiment, an amine compound is present in the solution
according to the invention in an amount from about 0.1% to about
10%, alternately from about 1% to about 10%, from about 0.5% to
about 5%, from about 0.5% to about 3%, from about 0.1% to about 2%,
or from about 1% to about 3%.
In one embodiment, the composition according to the invention may
also contain a surfactant. Examples of surfactants include, but are
in no way limited to, sodium laurel sulfate, sodium stearate,
epoxy-polyamide, and the like, or a combination thereof. In an
alternate embodiment, the composition according to the invention is
substantially free from surfactants.
In one embodiment, a surfactant is present in the solution
according to the invention in an amount from about 0.1% to about
10%, alternately from about 1% to about 10%, from about 0.5% to
about 5%, from about 0.5% to about 3%, from about 0.1% to about 2%,
or from about 1% to about 3%.
pH
The pH of the dilute aqueous solutions of phosphoric acid may vary
considerably from one formulation to another, and the optimum pH
can be readily ascertained by evaluating cleaning efficiency and
material compatibility at various pH levels. In particular,
different pH values are useful with different substrates. In one
embodiment, the pH of the solution is between about 1.5 and about
5, alternately between about 2 and about 4.5, between about 1.5 and
about 10, between about 1.5 and about 9, between about 2 and about
6, or between about 1.5 and about 6.
Substrates
The dilute aqueous solutions of phosphoric acid are advantageous
for cleaning residues from vias of varying aspect ratios and from
metal structures. The metal structures may be simple plugs of
metal, such as tungsten, or metal stacks including two or more of
titanium nitride, aluminum, copper, aluminum/copper alloy,
titanium, tungsten, tantalum, and other metals useful in
semiconductor fabrication, as well as mixtures or alloys thereof.
Additionally or alternately, the substrate may include (e.g., as at
least a portion of one or more layers) metal nitrides, metal
oxides, metal oxynitrides, and/or "metal alloys" with atoms or
compounds other than metals (e.g., phosphorus, boron, sulfur, or
the like).
Cleaning Process
The dilute aqueous solutions of phosphoric acid may be applied to
the semiconductor substrate through various methods. For instance,
application may be as a bath in which the substrate is submerged.
Alternately, the aqueous solution may be applied as a spray
directed to the surface of the substrate. Mechanical agitation,
ultrasonic and megasonic waves, bath circulation, rotation or other
motion of the substrate, and other additional steps may be used as
is well-known in the art.
The low volatility of the dilute aqueous solutions of phosphoric
acid permits high operating temperature, e.g., up to about
90.degree. C. or higher, of the cleaning process, although "room
temperature" operation of about 20.degree. C. to about 30.degree.
C. provides a good combination of cleaning efficiency and material
compatibility for most applications.
The time required for the cleaning process is dependent upon the
residue to be removed, operating temperature and method of
application. Typical time is from about 5 to about 30 minutes,
alternately from about 3 to about 30 minutes, from about 3 to about
15 minutes, from about 3 to about 20 minutes, from about 5 to about
10 minutes, from about 5 to about 15 minutes, or from about 5 to
about 20 minutes, and can be readily ascertained by evaluating
cleaning efficiency and material compatibility at various
times.
Considering that the removal of the post etch residue in the
presence of phosphoric acid is believed to be via the formation of
an intermediate phosphate complex, but without being bound to
theory, the presence of a quaternary ammonium or the formation of a
cation through the acid-base reaction may enhance the cleaning
ability of the blend. It is believed that this enhancement may
arise through electrostatic interaction between the cation from the
base and the anionic residue phosphate complex.
Furthermore, without being bound to theory, the investigation
indicated that residue removal is probably not by a proton
initiated dissolution mechanism, because of the poor cleaning
results obtained solutions containing only phosphoric acid and the
other acid compounds, even those other acids that were very strong.
It is surmised, therefore, that the cleaning ability of the
preferred solutions according to the invention is probably due
mainly to the chelating properties and dissolution ability of the
other acid component (e.g., in combination with phosphoric
acid).
A rinse step typically, although not always, follows the
application of the dilute aqueous solutions of phosphoric acid. The
rinse material may be water, alcohol such as isopropyl alcohol, a
water/alcohol blend, or a rinse material as described in U.S. Pat.
No. 5,981,454, the entire disclosure of which is incorporated
herein by express reference hereto. Use of a rinse step is
preferred, and water is the preferred rinse material.
EXAMPLES
Exemplary embodiments of the present invention will be illustrated
by reference to the following examples, which are included to
exemplify, but not to limit, the scope of the present
invention.
Examples 1 28
Dilute aqueous solutions of phosphoric acid as described in Table 1
and Table 2 have been used to clean plasma etch residues from
semiconductor substrates. The following abbreviations are used for
solution components:
TABLE-US-00001 TMAH--tetramethylammonium hydroxide EL--ethyl
lactate CHOL--choline hydroxide PPA--pyrophosphoric acid
DEHA--N,N-diethylhydroxylamine ABF--ammonium bifluoride
AEEA--2-(2-aminoethylamino)ethanol AF--ammonium fluoride
MSA--methanesulfonic acid EPA--epoxy-polyamide
Unless otherwise specified, all values delimited in the Tables of
these Examples, with the exception of pH values and corrosion and
cleaning ratings, are expressed in terms of weight percent.
Table 1 below provides compositions of examples 1 to 12.
TABLE-US-00002 H.sub.3PO.sub.4 Alkaline Other Example (%) Compound
% Comnpounds % pH 1 2 DEHA 0.94 2 2 AEEA 1.2 3 2 CHOL 0.99 2.1 4 2
HDA 0.65 ABF 0.02 5.2 EPA 0.12 5 2 HDA 0.65 ABF 0.02 5.2 6 3 HDA
0.75 AF 0.04 5 7 2 HDA 0.65 AF 0.04 5 EL 10.0 8 2 HDA 0.5 5 9 2
AEEA 1 2.8 10 6 CHOL 2.2 11 6 AEEA 2 12 6 CHOL 2.2 Glycolic 2
Table 2 below provides compositions of examples 13 to 28.
TABLE-US-00003 Example H.sub.3PO.sub.4 (wt. %) Other Acid % (wt.)
13 2 MSA 1.47 14 2 PPA 3.0 (pH = 0.8) 15 2 Fluorosilicic 0.24 16 2
Oxalic 2.0 17 4 Oxalic 2.0 18 6 Glycolic 1.0 19 3 Oxalic 2.0 20 3
Lactic 2.0 21 4 Lactic 2.0 22 3 Citric 2.0 23 4 Citric 2.0 24 3 PPA
0.5 25 3 Glycolic 2.0 26 6 Glycolic 2.0 27 3 PPA 2.0 28 3 PPA
4.0
The solution of Example 25 was used in a bath application to clean
plasma etch vias. The residue was removed after about 8 minutes at
about 30.degree. C. The cleaned residue from metal lines after
about 5 minutes at about 30 .degree. C.
The solution of Example 3 was used in a spray application in a
Semitool apparatus ma etch residue from metal stacks. The stacks
consisted of titanium nitride-per alloy-titanium-titanium nitride
on silica. Process conditions in the tool were about 30.degree. C.,
approximately 1 gallon per minute (GPM) flow rate, about 140 or
about 300 revolutions per minute (RPM), and application time of
about 5 or about 10 minutes. Residues were removed at both RPM
settings at both application times. No corrosion or pitting was
noted at about 5 minutes although slight pitting was noted at about
10 minutes.
The solutions of Examples 4 5 were used to clean metal stacks in a
Semitool as previously described. Residues were removed and no
corrosion or pitting was noted for either sample at both RPM
settings and both application times.
The solutions of Examples 3 5 were used in a spray application in a
Semitool apparatus to clean aluminum lines on a tantalum substrate.
Process conditions were the same as previously described. Residues
were removed and no corrosion or pitting was noted at both RPM
settings and both application times.
The solution of Example 3 was used in a spray application in an FSI
apparatus to clean plasma etch residue from metal stacks from three
sources. All of the stacks consisted of titanium
nitride-aluminum/copper alloy-titanium-titanium nitride on silica.
Process conditions in the tool were about 25 or 35 .degree. C.,
approximately 1 liter per minute (LPM) flow rate, about 400 RPM,
and application time of about 5 or about 10 minutes. For the stacks
from the first source, residues were removed at 25 .degree. C. at
about 10 minutes with no corrosion or pitting. For the stacks from
the second source, traces of residue remained but these likely
would be removed with longer application times; no corrosion or
pitting was noted. For the stacks from the third source residues
were removed after about 10 minutes at both temperatures, with no
corrosion or pitting observed.
The solutions of Examples 4 7 were used in a bath application at
about room temperature to remove plasma etch residues from metal
stacks from three sources. Residues were removed within about 5
minutes. No corrosion or pitting was noted after about 20
minutes.
The solutions of Examples 19, 20, 23, and 25 were used in a bath
application at room temperature to remove plasma etch residues from
champagne vias and metal lines. Residues were removed in process
times of about 3 15 minutes, and no corrosion or pitting was
noted.
All of the above-described process examples used a deionized water
(DIW) rinse following the cleaning step.
Examples 29 33 and Comparative Example 1
A series of dilute aqueous solutions of phosphoric acid and choline
hydroxide, Examples 29 33, were prepared as shown in Table 3 below
and used in a bath application to remove residue. Comparative
Example 1 shows the result of using a dilute aqueous solution of
choline hydroxide without any phosphoric acid present. Cleaning
efficiency was rated on a 0 10 point scale with 10 being complete
removal. Corrosion and pitting was rated on a 0 10 point scale with
0 being no corrosion and pitting.
TABLE-US-00004 TABLE 3 Phosphoric Choline Example pH Corrosion
Cleaning acid hydroxide 29 1.4 0 6 2 0 30 2 0 10 2 2.2 31 5 0.5 10
2 4.8 32 7 1 8 2 5.5 33 9 4 10 2 8 Comp. Ex. 1 12 10 10 0 2.2
Process time and temperature could be optimized for the solution
with pH from about 5 to about 9 to provide both complete cleaning
and acceptable corrosion and pitting. All of the above-described
process examples used a deionized water (DIW) rinse following
cleaning step.
Although the present invention is described with reference to
certain preferred embodiments, it is apparent that modification and
variations thereof may be made by those skilled in the art without
departing from the spirit and scope of this invention as defined by
the appended claims. In particular, it will be clear to those
skilled in the art that the present invention may be embodied in
other specific forms, structures, arrangements, proportions, and
with other elements, materials, and components, without departing
from the spirit or essential characteristics thereof. One skilled
in the art will appreciate that the invention may be used with many
modifications of materials, methods, and components otherwise used
in the practice of the invention, which are particularly adapted to
specific environments and operative requirements without departing
from the principles of the present invention. The presently
disclosed embodiments are therefore to be considered in all
respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims, and not limited
to the foregoing description.
* * * * *